IFPA rating is very volatile and I’d wager that it’s worse than using IFPA ranking. You’d have to normalize the rating over a period of time of you’d basically just be looking at the player’s last tournament performance.
Or use Match Play Ratings (MPR). It’s based on actual game results rather than the simulations IFPA ratings use. You can see how the Seattle team league combines MPR and IFPA ranking to assign a number between 1-6 for each player. It’s a good example of how to combine data from multiple sources to do division restrictions.
A lot of work though.
More information starting here and in the posts that follows: IFPA rating for team league salary cap?